Special Procedures For 208- -V Operation; Control Voltage Connections; Standard Connections; Transformer Protection - Carrier Performance 50VT-A24 Installation Instructions Manual

HIGH VOLTAGE
POWER LEADS
(SEE UNIT WIRING
LABEL)
3-PHASE SHOWN
1-PHASE USES
TWO POWER
EQUIP GR
LEADS
CONTROL BOX
LOW-VOLTAGE
POWER LEADS
)
(SEE UNIT
WIRING LABEL
SPLICE BOX
Fig. 9 - - High- - and Control- -Voltage Connections
Single phase units:
1. Run the high- -voltage (L1, L2) and ground lead into the
control box.
2. Connect ground lead to chassis ground connection.
3. Locate the black and yellow wires connected to the line side
of the contactor.
4. Connect field L1 to black wire on connection 11 of the
compressor contactor.
5. Connect field wire L2 to yellow wire on connection 23 of
the compressor contactor.
Three- -phase units:
1. Run the high- -voltage (L1, L2, L3) and ground lead into the
control box.
2. Connect ground lead to chassis ground connection.
3. Locate the black and yellow wires connected to the line side
of the contactor.
4. Connect field L1 to black wire on connection 11 of the
compressor contactor.
5. Connect field wire L3 to yellow wire on connection 13 of
the compressor contactor.
6. Connect field wire L2 to blue wire from compressor.
Special Procedures for 208- - V Operation
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal
injury or death.
Before installing or servicing system, always turn off main
power to system. Tag the disconnect switch with a suitable
warning label. With disconnect switch open, move black
wire from transformer (3/16 in.) terminal marked 230 to
terminal marked 208. This retaps transformer to primary
voltage of 208 vac.

Control Voltage Connections

NOTE: Do not use any type of power- -stealing thermostat. Unit
control problems may result.
Use no. 18 American Wire Gage (AWG) color- -coded, insulated
(35°C minimum) wires to make the control voltage connections
POWER
SUPPLY
FIELD-SUPPLIED
FUSED DISCONNECT
WHT(W1)
W1
VIO (W2)
W2
YEL(Y)
Y
GRN(G)
G
THERMOSTAT
RED(R)
R (TYPICAL)
BRN(C)
C
ORN(O)
O
BLU(DH)
DH
GRA(Y2)
3-Phase
Only
A09071
between the thermostat and the unit. If the thermostat is located
more than 100 ft (30.5 m) from the unit (as measured along the
control voltage wires), use no. 16 AWG color- -coded, insulated
(35° C minimum) wires.

Standard Connections

Locate the eight (nine on 3- -phase) low voltage thermostat leads in
24 volt splice box. See Fig. 9 for connection diagram. Run the
low- -voltage leads from the thermostat, through the control wiring
inlet hole grommet (Fig. 2 and 3), and into the low- -voltage splice
box. Provide a drip loop before running wires through panel.
Secure and strain relief all wires so that they do not interfere with
operation of unit. A gray wire is standard on 3- -phase units for
connection to an economizer.
If an accessory electric heater is installed, low voltage leads from
heater must be connected to factory supplied control leads from
Indoor Fan Board P4 connector. Factory wires are provided for
electric heat staging W1 and W2 (W2 and W3 on IFB). If room
thermostat has only one stage of supplemental heat, connect white
and violet wires shown in Fig. 9 to second stage heat field wire.
Some electric heaters have four control wires (plus common wire).
Consult unit wiring diagram and electric heater wiring diagram for
additional details.

Transformer Protection

The transformer is of the energy- -limiting type. It is set to withstand
a 30- -second overload or shorted secondary condition. If an
overload or short is present, correct overload condition and check
for blown fuse on Interface Fan Board. Replace fuse as required
with correct size and rating.

Accessory Electric Heaters Installation

Electric heaters may be installed with the 50VT- -A units per
instructions supplied with electric heater package. See unit rating
plate for factory- -approved electric heater kits.

Sequence of Operation

a. CONTINUOUS FAN
(1.) Thermostat closes circuit R to G energizing the
blower motor for continuous fan.
b. COOLING MODE
(1.) If indoor temperature is above temperature set
point, thermostat closes circuits R to G, R to Y and
R to O- -The unit delivers cooling airflow.
c. ELECTRIC HEATING MODE
(1.) Thermostat closes circuit R to W/W1, or W2 and R
to G. There are no on or off delays.
d. HEAT PUMP HEATING MODE
(1.) Thermostat closes circuits R to G and R to Y. The
compressor, indoor and outdoor fans are energized.
e. HEAT PUMP HEATING WITH AUXILIARY
ELECTRIC HEAT
(1.) Thermostat closes circuits R to G, R to Y and R to
W/W1 or W2. The compressor, indoor and outdoor
fans are energized, as well as the electric heat
relays.
f. DEFROST MODE
The defrost mode is automatically energized by the
defrost board during heating mode. The defrost board
energizes "O" (reversing valve) and "W2" (electric
heat). It also de- -energizes the outdoor fan. When defrost
is complete, unit will return to heating mode. If room
thermostat is satisfied during defrost, unit will shut
down and restart in defrost on next call for heat.
9